1. Field of the Invention
The present invention relates to an intermediate lens barrel to be mounted between an objective lens barrel and a camera. In particular, the present invention relates to such intermediate lens barrel provided with means for transmitting a signal from the objective lens barrel to the camera.
2. Description of the Prior Art
There is known and used in the art an objective lens barrel is which is provided with signal means indicative of information specific to the objective lens such as its minimum F-number or focal length. Said signal means is provided on a mount formed on the lens barrel for connecting the lens barrel to a camera. For example, mention is made of U.S. Pat. No. 4,269,497. In the lens barrel disclosed therein, a groove is formed on the mount. The groove has a particularly determined depth in the direction of the optical axis. The groove depth is indicative of the above mentioned information of the objective lens. When the lens barrel is mounted on a camera, a movable and projectable pin provided on the mount of the camera is shifted corresponding to the depth of the groove on the lens barrel. Thus, information is transmitted from the lens barrel to the camera. Mounting of the objective lens barrel on a camera and demounting it from the camera is effected by means of a known bayonet mount mechanism. Therefore, the lens barrel must be rotated about the optical axis by a determined angle relative to the mount of the camera for mounting or for demounting. To assure an easy engagement of the pin in the groove or an easy disengagement of the pin from the groove during the rotation for mounting or demounting, the groove is tapered in the circumferential direction of the lens barrel. An intermediate lens barrel to be mounted in between such objective lens barrel and camera is therefore required to have a device for transmitting the information of the objective lens barrel to the camera.
For such signal transmission device it is required to be able to smoothly engage with the movable pin projecting from the camera not only when the intermediate lens barrel is mounted on the camera after connecting the objective lens barrel with the intermediate lens barrel but also when the intermediate lens barrel is mounted on the camera before connecting the objective lens barrel to the intermediate lens barrel.